I would go somewhere new, because that would be better for your personal and professional development, in my opinion. I'm in a similar situation, and although the grad students and professors at my undergrad university are amazing, I'm already really familiar with their take on my field. I'm sure I would still have a lot to learn if I stayed behind, but I think a new place would allow more room to be exposed to new ideas, new perspectives, etc. It'll ultimately give you a more complete understanding of your field.
Is it a PhD program? Ten years is a long time to be associated with one university while you're still young.